Pressure relief system for an aerosol container

ABSTRACT

A metal container that is adapted to hold a pressurized product for dispensing through a valve mounted on the container. The container has a safety venting system therein, whereby the product may be vented from a filled pressurized container through the system when an increase in internal pressure threatens to blow an end off the container. The venting system comprises a plurality of scores formed in the upper seam where the container body is jointed to the dome closure of the container. When the internal pressure of a filled container increases sufficiently the periphery of the dome buckles outwardly causing the residual of the scores to fracture and thus produce a plurality of vents to permit the highly pressurized contents of the sealed container to safely escape and prevent end blow off.

United States Patent Giocomo et al.

[ Jan. 22, 1974 PRESSURE RELIEF SYSTEM FOR AN AEROSOL CONTAINER [75] Inventors: James Donald Giocomo,

Schaumburg; Harry Anthony Grosso, Wheeling, both of 111. [73] Assignee: American Can Company,

Greenwich, Conn.

[22] Filed: June 8, 1972 [21] Appl. No.: 261,126

Related US. Application Data [63] Continuation of Ser. No. 75,470, Sept. 25, 1970,

abandoned.

52 US. Cl. 222/397, 222/541 [51] Int. Cl B65d 83/00 [58] Field of Search 222/183, 394, 397, 54; 220/44, 220/67, 89 D; 122/504 [56] References Cited UNITED STATES PATENTS 3,450,305 6/1969 Kinnavy et a1 222/397 X 2,795,350 6/1957 Lapin 220/44 R 3,029,981 8/1962 Webster et al.. 222/397 X 3,292,826 12/1966 Abplanalp 222/397 3,519,171 7/1920 Kinnavy 222/394 3,477,614 11/1969 Runge 222/541 X 3,227,304 1/1966 Asbury 222/541 X 3,074,602 1/1963 Shillady et al. 222/397 3,029,987 4/1962 Gronemeyer.. 222/541 3,680,743 8/1972 Reinnagel 222/397 [57] ABSTRACT A metal container that is adapted to hold a pressurized product for dispensing through a valve mounted on the container. The container has a safety venting system therein, whereby the product may be vented from a filled pressurized container through the system when an increase in internal pressure threatens to blow an end off the container. The venting system comprises a plurality of scores formed in the upper seam where the container body is jointed to the dome closure of the container. When the internal pressure of a filled container increases sufficiently the periphery of the dome buckles outwardly causing the residual of the scores to fracture and thus produce a plurality of vents to permit the highly pressurized contents of the sealed container to safely escape and prevent end blow off.

5 Claims, 9 Drawing Figures INVENTORS i JAMES DONALD GIOCOMO 4 m HAIRRY ANTHONY cnosso v 4 /f f in Z A y zW/QX WK ATTORNEY PRESSURE RELIEF SYSTEM FOR AN AEROSOL CONTAINER This is a continuation of application Ser. No. 75,470, filed Sept. 25, 1970 now abandoned.

BACKGROUND OF THE INVENTION The present invention relates generally to a metal aerosol container having a pressure relief system whereby the internal contents of the container may be vented therefrom when the internal pressure rises sufficiently to a level threatening blowing an end off the container. More particularly this invention relates to a two or three piece metal aerosol container having a simple venting system to eliminate explosion of a filled aerosol container when the internal pressure rises considerably, which may be encountered during excessive heating of the container.

For many years pressurized aerosol containers have been marketed to the general public. These containers usually comprise a three piece metal container having therein a product to be dispensed, together with a propellant that provides the internal pressure necessary to dispense the product through a valve mounted on the container. Products such as foods, cosmetics, insecticides, etc. have been packaged in these types of containers with considerable success.

However, due to the fact that the container is pressurized, problems have been encountered when the internal pressure of the container rises rapidly above that pressure to which the container construction has the capacity to hold. In some instances this rapid increase in internal pressure, resulting from rapid heating, has caused the container to explode. This has sometimes occurred in warehouse fires where large quantities of these aerosol containers are stored. In some cases, firemen have been injured during such explosions and in some instances firemen are unable to control the flames since they cannot approach them.

Over the years many attempts have been made to design containers having pressure relief systems in order to eliminate the possible explosive danger from pressurized aerosol containers. Many of these constructions include specialized valves which rupture upon heating or when exposed to extremely high internal container pressures. However, in general, such constructions have greatly increased the cost of these containers to such a degree that they are not economically practical.

Other safety features have included weak areas in the container body such that under excessive internal pressure the weakened portion would rupture and permit venting of the container contents. One such construction is shown in US. Pat. No. 3,074,602. In this patent a pressure sensitive area is formed in the valve cup such that when the dome of the container everts or buckles due to high internal pressure, venting will occur through a rupture produced in the pressure sensitive area. However positioned, this weakened portion would not necessarily rupture when the dome of the container buckles and venting through the single area of failure would not necessarily be rapid enough to pre-.

vent explosion of the container.

In US. Pat. No. 2,795,350 a nick is formed in the periphery of the body closure of the container where it forms a double seam with the container body. In this two piece aerosol container extremely high pressure supposedly causes concave bottom wall to buckle and rupture the nick to form a vent through the bottom of the container. However, in the usual case the bottom would buckle and blow off before venting through the nick would relieve the high internal pressure of the container.

The new safety feature described in this invention will protect against can failures in the packing and marketing of aerosol cans. If excessive internal pressure develops in a filled can due to an unusual situation, the safety feature would activate rapidly and provide adequate venting to completely vent the container contents before bottom end blow ofi could occur.

Full cans will vent if excessive pressure develops in the can due to misuse. This might involve placing the can on a hot stove or radiator, near a hot iron, or in the glove box, trunk, or window of a car sitting out in the sun.

Generally, partially tilled cans will also vent under the conditions mentioned above; however, near-empty cans may fail at the side seam in typical three piece metal cans before the pressure required to activate the safety feature is generated under prolonged exposure to intense heat.

Aerosol cans which are considered empty or nearly empty usually contain a small amount of residual product and propellant. These small amounts are sometimes not sufficient to generate the pressure needed to activate the safety feature when the can is incinerated. Under the intense heat of incineration, some of these cans will vent or rupture at the side seam. This is due to the fact that the side seam is adhered with a solder or relatively low temperature material. The side seam rupture will occur at pressures below the pressure required to buckle the dome and thus before activation of the safety venting feature. This failure, although dangerous, is less violent than blow-off of the bottom end.

Certain products in cans which are thrown away as empty or nearly empty will generate sufficient pressure to activate the safety feature when incinerated. This is entirely dependent upon the amount and type of product and propellant remaining in the can. Full or partially full cans will also vent safely if they are incinerated.

The instant aerosol pressure relief system effectively vents excess internal pressure in all filled cans before the bursting point is reached. Under conditions of intense heat, as in incinerators, empty or near empty cans may fail, but the intensity of the failure is dramatically reduced.

SUMMARY OF THE INVENTION A pressure relief system for an aerosol container forming the present invention comprises a tubular metal container adapted to hold a pressurized product that is dispensed through a valve mounted on the container. The container has a safety venting system therein, whereby the product may be vented from a filled pressurized container through the system where an increase in internal pressure threatens to cause bottom end blow-off. The container comprises a tubular metal body having a closure seamed to one end and the opposite end has a metal dome seamed thereto, the dome being adapted to receive a valve to close the container. A plurality of scores are formed in the periphery of the dome. The scores penetrate only partially through the metal of the dome at the seam which forms a hermetic seal with the container body. Thus, when the internal pressure within the sealed container increases and threatens to cause the container bottom end to blow-off the periphery of the dome buckles outwardly, causing the residual of the scores to fracture and produce a plurality of vents to permit the highly pressurized contents of the sealed container to safely escape and thus prevent bottom end failure.

DESCRIPTION OF THE DRAWINGS FIG. 4 is an enlarged sectional view taken substantially along the line 44 in FIG. 3;

' FIG. 5 is an enlarged fragmentary sectional view of the double seam formed by the periphery of the dome and the top of the container body;

FIG. 6 is an enlarged fragmentary side elevational view of the seam shown in FIG. 5 more fully illustrating a vent score;

FIG. 7 is an enlarged partial sectional view similar to FIG. 5 but illustrating the vent score on the interior of the periphery of the dome;

FIG. 8 is an enlarged fragmentary sectional view illustrating the periphery of the dome after high internal pressure has buckled the dome and fractured the vent score to form a safety pressure relief vent; and

FIG. 9 is an enlarged fragmentary side elevational view illustrating the ruptured score safety vent after buckling of the dome.

DESCRIPTION OF THE PREFERRED EMBODIMENT As a preferred or exemplary embodiment of the instant invention FIGS. 1 and 2 show a container, generally designated 12, comprising a tubular metal body 14 having a side seam 15. The side seam is generally sealed with solder, as is well known in the art, although it may also be welded. Closing the bottom of the container is an end 16 hermetically seamed to the bottom of the body 14 by a seam 18.

As the container 12 will ultimately be utilized as an aerosol container, a dome 20 is seamed to the top of the body 12 by a double seam 22. The upper end of the dome has an orifice 23 defined by a top curl 24. After filling with product and a suitable propellant, a valve cup, not shown, is placed into the orifice 23 and a suitable dispensing valve, also not shown, is positioned within the valve cup to seal the container 12 and to permit dispensing of the product and propellant from the container 12.

A plurality of radial scores 26 are formed in the periphery of the dome in the top of the double seam 22. As may be better seen in FIGS. 3-6 the scores 26 are narrow grooves formed in the periphery of the dome 20 and penetrate only partially through the metal of the dome 20. For example, a score 26 has a depth of approximately 0.0l0 inch for a total metal thickness of 0.015 inch leaving a solid metal residual 30 of 0.005

inch. The developed length of the score is approxi-' mately 0.125 inch. As shown in FIG. 4 the angle of the score 26 is approximately 90 and it is desireable that this angle not be below As will be noted the bottom 28 of the score 26 has a radius and is rounded in cross sectional appearance. This provides greater integrity and prevents premature cracking through the residual 30 of the material which would result in leakage of product and propellant from the container 12.

As can be seen in FIG. 3, the dome 20 has a countersink 32 comprising a portion of the double seam 22 and countersink radius 34 adjacent the seam area connecting the top of the body 14 with the dome 20. In forming this double seam 22, the top of the body 14 terminates in a flange 36 which fits within a curl 38 which forms the peripheral edge of the dome 20. In forming the double seam the flange 36 is interfolded with the curl 38 to hermetically seal and close the container 12 as the double seam 22 is formed. In addition, a small amount of sealing compound 40 is positioned along the interior wall of the curl 38 to provide a hermetic seal in forming the double seam 22. A similar type of double seam may be used to form the seam 18 at the bottom of the container l2.

THe fully formed double seam 22, shown in FIG. 5, thus hermetically seals the dome 20 to the body 14. Spaced about the top of the double seam 22 are a plurality of the scores 26 which extend radially within the top of the double seam 22.

In a modified construction, shown in FIG. 7, a plurality of radial scores 42 are formed on the interior of the periphery of the dome 20. Thus, when the double seam 22 is formed by the flange 36 and curl 38 the score is hidden by being entirely within the double seam 22. In certain instances this has aesthetic advantages in that the multiplicity of scores 42 are not seen by the user as are the exterior scores 26. However, either will function in the manner described hereinafter to provide a pressure relief system for a filled container 12.

As is well-known, there is some controversy in the usage of aerosol containers due to the fact that they are under high internal pressures and subject to abusive use. To date, the various concepts for pressure relieving an aerosol container have proved uneconomical. Any relief concept must function under both normal use conditions and under uncontrollable use conditions which violate general precautionary labeling. Some abusive conditions would include storage in direct sunlight, storage in enclosed automobiles during summer months and warehouse fires.

Also, the relief concept must allow function of the container under controllable use conditions in violation of precautionary labelling so long as the temperature does not exceed that temperature that could result in rupture of the container.

The greatest danger when aerosol containers are subject to temperature abuse is when the bottom of the container everts or buckles under extreme internal pressure and blows off. Due to the fact that the bottom is constructed to withstand extreme internal pressures, when these pressures are reached the bottom end may buckle and separate from the remainder of the container possibly resulting in propelling parts of the container about the immediate area.

A secondary type of failure encountered when internal pressure increases over the maximum allowable by the container construction is a side seam rupture which generally results from exposure to high temperatures. The side seam failure is dependent upon exposure temperature, the position of the container with respect to the heat source, the type of product and propellant packed in the container, the quantity of product and propellant remaining in the container, and the container size. For a container of average size such as those of 3 inches in diameter and approximately 7 9/16 height, it has been found that the relief concept must be capable of releasing 14 cubic feet per minute of internal gas at 200 psig. Less release capacity is required for smaller containers and vent capacity is strictly dependent upon volumetric capacity.

Following the teachings of U.S. Pat. No. 2,795,350, a nick was formed in the double seam securing the bottom closure to a container body. Upon heating the can in a fire failure was obtained as the bottom end buckled and the can exploded before venting could occur. When a single nick was placed in the top seam of a three-piece container and the container filled with Freon 12 propellant, another test was run wherein the can was placed in an open fire. The top end buckled, but the Freon 12 and the product therein could not escape rapidly enough. Thus, the top end of the container blew off in this instance. In another, the side seam failed explosively, whereas in a third test the bottom blew off. In all cases venting began through the fractured nick but explosive failure occurred in all instances.

Thus, a single venting means is not adequate due to the fact that the top dome does not vent rapidly enough. Instead the pressure within the container will continue to increase rapidly until it exceeds the strength of the container construction. When this point is reached the container can fail in an uncontrolled manner. In such instances, an explosion could occur and failure could occur in either the top, bottom or side seam.

As was mentioned hereinbefore, tests have indicated that a minimum venting capacity must be present in each container to insure safety and functional operation of the venting system. In tests where fifty cans without a relief system and containing propellant were subjected to an incinerator fire, fourteen exhibited bottom end blow off while twenty seven produced side seam failures after the top end had buckled with projectiles being thrown from the fire about the immediate area. In only nine instances of the fifty tests were no projectiles ejected from the fire.

When utilizing the venting pressure relief system described hereinafter it was possible to increase the degree of venting and decrease the end blow off failures to less than 10 percent for filled containers and to prevent ejection of container parts from the incinerator fire completely.

It can be seen in FIGS. 8 and 9 that when the internal container pressure increases sufficiently the dome 20a buckles and the countersink 32a and countersink radius 340 also deform as the double seam 22 partially unfolds raising the radial score 26a away from the seam andrupturing it to form a vent 44. This vent 44 permits pressurized product and propellant from within the container 12 to escape and safely vent the container.

As may be seen from the drawings, a number of radial scores have been formed in the double seam 22. This is to insure that no matter where the dome 20 begins buckling due to increased internal pressure, a vent 44 will be formed almost immediately and as the buckling continues about the periphery of the dome 20 additional vents 44 will form about the periphery of the dome 20- as additional radial scores 26 are deformed and fractured.

It has been found that at 200 psig inside a 300 X 709 can, 12 radial scores will vent from 14 to 21.5 cubic feet per minute of gas. Eight radial scores per end will vent from 1 1.5 to 14 cubic feet per minute of gas, and six radial scores per end will vent from 10 to 12.5 cubic feet per minute of gas. In these tests air temperature was about 78F. Thus it can be seen for a container of such size a minimum of 8 score vents will permit reasonably safe evacuation of the internal gases within an overpressurized filled container, although at least 12 score vents are preferred for greater reliability.

It must be noted that these tests were all conducted with filled containers containing sufficient amounts of propellant to insure rapid buckling of the dome 20 when pressure was increased at a relatively rapid rate from external heating. However, with partially filled or near empty containers the external heat might be sufficient to melt the conventional solder side seam so that failure could occur at the side seam rather than by buckling the dome 20 to form the vents 44. But, as has been indicated, failure of the side seam is far less serious than failure at the bottom where blow off could cause serious damage if container parts are propelled about the area.

It can thus be seen that a sufficient degree of venting must be present in the container to permit rapid exhaustion of the propellant and product through the vent system before end blow off occurs. The single vent shown in the prior art has been found to be insufficient to insure such rapid exhaustion as is necessary to prevent end blow off of aerosol containers when subjected to high internal pressures, frequently encountered under abuse of systems. In addition, the geometric shape of the score is most important in insuring rupture and proper formation of the vent 44 under buckling conditions while guaranteeing proper hermetic sealing of the container during normal use.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely an exemplary embodiment thereof.

We claim:

1. A metal container adapted to hold a pressurized product that is dispensed through a valve mounted on said container, said container having a safety venting system therein whereby the contained product is vented from the container through said system when an increase in internal pressure threatens to cause rupture of said container, comprising:

a tubular metal body closed at one end;

a metal, domed end member attached to the opposite end by a double seam having a countersink segment, said countersink segment having a straight line portion, and said domed end member being adapted to receive said valve to close said container;

a plurality of score lines in a peripheral portion of said domed end member, said score lines being in at least a part of the straight line portion of the countersink segment and extending to at least the midpoint of the top portion of the double seam and is formed by a separate end double seamed to the metal body.

3. The container of claim 2 wherein the separate end is concave.

4. The container of claim 2 wherein the score lines are located on the interior of the domed end member.

5. The container of claim 1 wherein the score lines are uniform. 

1. A metal container adapted to hold a pressurized product that is dispensed through a valve mounted on said container, said container having a safety venting system therein whereby the contained product is vented from the container through said system when an increase in internal pressure threatens to cause rupture of said container, comprising: a tubular metal body closed at one end; a metal, domed end member attached to the opposite end by a double seam having a countersink segment, said countersink segment having a straight line portion, and said domed end member being adapted to receive said valve to close said container; a plurality of score lines in a peripheral portion of said domed end member, said score lines being in at least a part of the straight line portion of the countersink segment and extending to at least the midpoint of the top portion of the double seam and penetrating only partially through the metal of said domed end member, whereby when the internal pressure within the sealed container increases and threatens to cause rupture of said container, said domed end member will buckle outwardly causing the residual of said scores to fracture to produce a plurality of vents to permit the highly pressurized contents of said sealed container to escape safely therefrom.
 2. The container of claim 1 wherein the closed end is formed by a separate end double seamed to the metal body.
 3. The container of claim 2 wherein the separate end is concave.
 4. The container of claim 2 wherein the score lines are located on the interior of the domed end member.
 5. The container of claim 1 wherein the score lines are uniform. 